GAS DENSITY RATIO DETECTION DEVICE, CONCENTRATION DETECTION DEVICE AND FUEL VAPOR TREATMENT DEVICE

摘要

PROBLEM TO BE SOLVED: To provide a gas density ratio detection device accurately detecting density ratio of a plurality of kinds of gas. SOLUTION: This device is provided with: a measurement passage 24 having a plurality of kinds of gas flowing in from an upstream side end part at different timing; a pump communicating to a downstream side end part of the measurement passage 24 to reduce pressure in the measurement passage; an orifice 14 provided in a middle part of the measurement passage 24 and reducing passage area of the measurement passage 24; an exfoliation suppression means 16 suppressing exfoliation of the plural kinds of gas from an inner wall surface 24c of the measurement passage 24 at the downstream side more than the orifice 14; a measurement means measuring pressure difference between both ends of the orifice 14 or flow rate of gas passing through the orifice 14 under a condition where pressure in the measurement passage is reduced by the pump; and a density ratio calculation means calculating density ratio of the plural kinds of gas based on pressure difference or flow rate measured by the measuring means. COPYRIGHT: (C)2007,JPO&INPIT